On the modelling and regulation of the cardiovascular system: Applications in 1D & 3D

Baroreceptors are sensory cells that help the body to keep a constant aortic pressure by regulating cardiovascular parameters. The cardiovascular system can be modelled by several methods, comprising lumped parameter models which represent important parts of the body, or 3D models which are used to observe the local flow and pressure distribution. Current state of the art of modelling couples these models together in order to get more accurate 3D solutions in a computationally tractable manner. In the first part of this work, baroreflexes have been modelled using fuzzy controllers and inserted in a lumped parameter cardiovascular loop. Simulation results have shown the control of the system: The aortic pressure coming back to normal values after a slight perturbation imposed to the model, as long as this perturbation is within a physiological range. For strong perturbations, a limit of the baroreceptors was reached, corresponding to the natural regulation limit of the body. The second part of this work was to study the influence of boundary conditions imposed on the 3D models, with the final aim to couple the lumped parameter cardiovascular loop with a 3D model. Results showed different velocity and pressures distributions according to different boundary conditions. The most important result was the coupling of a 3D vessel with a cardiovascular loop, where several heart cycles were simulated: pressures and flows curves were stable over the different heart cycles. Barocontrollers were then inserted in this coupling, and showed the possibility to control the system if the initial pressure is higher than normal. Pressure regulation of a 1D-3D coupling model has been made. Next step could consist of replacing the straight pipe by the aortic arch, with some adjustments to the lumped parameter model. Moreover, an alternative 3D part of the cardiovascular loop, such as a valve, could be inserted in the system